This is a note to let you know that I've just added the patch titled powerpc: Reintroduce is_kvm_guest() as a fast-path check to the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: powerpc-reintroduce-is_kvm_guest-as-a-fast-path-chec.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 297501a8e68937882c03890ab92ffdb1e6273a6e Author: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx> Date: Wed Dec 2 10:34:55 2020 +0530 powerpc: Reintroduce is_kvm_guest() as a fast-path check [ Upstream commit a21d1becaa3f17a97b933ffa677b526afc514ec5 ] Introduce a static branch that would be set during boot if the OS happens to be a KVM guest. Subsequent checks to see if we are on KVM will rely on this static branch. This static branch would be used in vcpu_is_preempted() in a subsequent patch. Signed-off-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx> Acked-by: Waiman Long <longman@xxxxxxxxxx> Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20201202050456.164005-4-srikar@xxxxxxxxxxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/arch/powerpc/include/asm/kvm_guest.h b/arch/powerpc/include/asm/kvm_guest.h index d7749ecb30d49..2fca299f7e192 100644 --- a/arch/powerpc/include/asm/kvm_guest.h +++ b/arch/powerpc/include/asm/kvm_guest.h @@ -7,8 +7,18 @@ #define _ASM_POWERPC_KVM_GUEST_H_ #if defined(CONFIG_PPC_PSERIES) || defined(CONFIG_KVM_GUEST) +#include <linux/jump_label.h> + +DECLARE_STATIC_KEY_FALSE(kvm_guest); + +static inline bool is_kvm_guest(void) +{ + return static_branch_unlikely(&kvm_guest); +} + bool check_kvm_guest(void); #else +static inline bool is_kvm_guest(void) { return false; } static inline bool check_kvm_guest(void) { return false; } #endif diff --git a/arch/powerpc/include/asm/kvm_para.h b/arch/powerpc/include/asm/kvm_para.h index 6fba06b6cfdbc..abe1b5e82547b 100644 --- a/arch/powerpc/include/asm/kvm_para.h +++ b/arch/powerpc/include/asm/kvm_para.h @@ -14,7 +14,7 @@ static inline int kvm_para_available(void) { - return IS_ENABLED(CONFIG_KVM_GUEST) && check_kvm_guest(); + return IS_ENABLED(CONFIG_KVM_GUEST) && is_kvm_guest(); } static inline unsigned int kvm_arch_para_features(void) diff --git a/arch/powerpc/kernel/firmware.c b/arch/powerpc/kernel/firmware.c index c3140c6084c93..c9e2819b095ab 100644 --- a/arch/powerpc/kernel/firmware.c +++ b/arch/powerpc/kernel/firmware.c @@ -22,6 +22,7 @@ EXPORT_SYMBOL_GPL(powerpc_firmware_features); #endif #if defined(CONFIG_PPC_PSERIES) || defined(CONFIG_KVM_GUEST) +DEFINE_STATIC_KEY_FALSE(kvm_guest); bool check_kvm_guest(void) { struct device_node *hyper_node; @@ -33,6 +34,7 @@ bool check_kvm_guest(void) if (!of_device_is_compatible(hyper_node, "linux,kvm")) return false; + static_branch_enable(&kvm_guest); return true; } #endif